DITISIOX OF HORTICULTURE 639 



SESSIONAL PAPER No. 16 



centage of bloom injured in botli cases. The count showed that over GO per cent of 

 the bloom outside the heated area was ruined by frost, while only 30 per cent of the 

 bloom inside the heated area was affected. In other words, the injury outside the 

 heated area was twice as great as the injury inside. 



From the foregoing evidence in conjunction with two previous seasons' results, 

 there is no hesitation in recommending orchard heaters for the purpose of preventing 

 frosts in orchards. There is, however, an element of chance in connection with 

 ground crops, such as strawberries. In addition to the difficulty of holding the tem- 

 perature on the ground to a point above freezing, there is also the disadvantage and 

 danger of the heaters boiling over, in which case a number of plants are bound to be 

 seriously damaged. Furthermore, if straw is present in the bed, injury from fire is 

 liable to result when a pot boils over. 



As orchard heaters, therefore, do not appear to be the most perfect means of pro- 

 tecting ground crops, a preliminary experiment with cheese cloth covers was conducted. 

 It was found that by suspending cheese cloth at a foot above the ground, a difference 

 of from 4 to 6 degrees in night temperature oould be effected. The cheese cloth cover 

 seemed sufficient to retain a large portion of the soil heat which would otherwise have 

 radiated into the atmosphere. It was also found that if the cover was left on during 

 the day, it did not prove so effective at night, due to the fact no doubt, that when the 

 cover was off in the day time, it gave the soil a better opportunity to absorb the sun's 

 heat, thus giving the soil more reserve heat to be held in check by the cover at night. 

 These cheese cloth covers are used by cranberry growers, and it is intended to try them 

 out on a large scale this coming year at Ottawa. From the present information, 

 it appears to be the most practical means of protecting strawberries that has yet been 

 devised. 



TYPES OF HEATER. 



Six different styles of heater were used and tested during the past season, and 

 from these tests the following recommendations are made for those who contemplate 

 the purchase of heaters : — 



1. Select a heater of large capacity, not less than four gallons. 



2. Select the style which has a good draft control. Proper control of draft 

 is very important, for it allows the oi)erator to increase or decrease the fuel 

 consumption, as he desires, thus increasing or decreasing the amount of heat 

 given off per hour. 



3. Round heaters are preferable to square or longitudinal ones, as they do 

 not warp so readily. 



SELF-LIGHTDsG HEATER. 



Among the different styles of heater was one which, it was claimed would light 

 itself at any temperature for which it was set. So far, our experience with these 

 heaters is not such that they can be recommended. This particular style had a cover 

 with a sensitive diaphragm that contracted as the temperature fell, thus liberating an 

 iron arm which scratched a match, the match in turn lighting a long wick. This wick 

 was used to tie the cover to the heater and as soon as burned off would thus release 

 the cover, which, being attached to the heater by a tight spring on the opposite side, 

 would thus fly off. The wick with a cork float attached would then fall into the oil 

 and ignite it. On several occasions these heaters worked all right, but two factors 

 rendered them unreliable. The first of these was, if the heaters were left in the field 

 over nigfet ready for work, the condensation, due to the difference between night and 

 day temperature, would render the match wet and useless, or that when the spring was 

 released the match would not ignite. This can only be prevented by daily examin- 

 ation, which is not practicable. The other objection is that all heavy fuel oils require 



Ottawa. 



